Alternative representation of GreenFunction boundaries in plots

[pablosanjose]

This replaces the boundary representation of GreenFunctions with translucent boxes over boundary cells and sites, in red by default. :boundarycolor and :boundaryopacity control their appearance. Also hide = :boundary removes them from the plot.

julia> g = LP.honeycomb() |> hopping(1, range = 1) |>
           attach(nothing, region = RP.circle(1, SA[2,3])) |> attach(nothing, region = RP.circle(1, SA[3,-3])) |>
           greenfunction(GS.Bands(subdiv(-π, π, 13), subdiv(-π, π, 13), boundary = 2=>-3));

julia> qplot(g, inspector = true, hide = nothing, children = (; sitecolor = :blue))

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 82.22222% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 92.35%. Comparing base (2c6ebdc) to head (1396e22).
Report is 1 commits behind head on master.

Files	Patch %	Lines
src/solvers/selfenergy/schur.jl	0.00%	5 Missing ⚠️
src/apply.jl	85.71%	1 Missing ⚠️
src/show.jl	50.00%	1 Missing ⚠️
src/types.jl	80.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #255      +/-   ##
==========================================
+ Coverage   92.31%   92.35%   +0.04%     
==========================================
  Files          36       36              
  Lines        5883     5901      +18     
==========================================
+ Hits         5431     5450      +19     
+ Misses        452      451       -1     

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[pablosanjose]

Note: in 1D lattices, the cells have no "volume", so they cannot be shaded. However, we still have boxes over boundary sites, here at x = -2